In related art digital offset lithographic printing systems, a dampening system applies a thin layer of fountain solution onto a surface of a digital offset imaging plate. An imaging system then evaporates the fountain solution film in an image area using a high power laser. A latent image is formed on the surface of the digital offset imaging plate. The latent image corresponds to a pattern of the applied fountain solution that is left over after evaporation.
An inking system may be used to apply a uniform layer of ink over a surface layer of the imaging plate. Typically, ink supplied on an inker form roll of the inking system is depleted from the form roll as the ink is transferred from the form roll onto the imaging plate. As a portion of the imaging plate surface containing the latent image passes through the inking system, the ink deposits onto the plate regions where the laser has vaporized the fountain solution. Conversely, ink is rejected by the plate regions where fountain solution remains. The resulting ink image is then transferred to paper or other print media via pressure.
Ink from the inker form roll may split onto the imaging member during ink transfer, leaving behind some ink on the form roll that may lead to uneven ink thereon. During the supplying of ink onto the form roll, not all areas on the form roll are covered with the same thickness of ink. Printing irregularities can result if an ink layer on the form roll is uneven and has areas of barely-layered ink that cause corresponding lighter areas in image prints.
To offset this problem, the inker form roll may be an anilox member, such as an anilox roll. However, one drawback for anilox rolls is non-uniform ink deposition on a micro scale. Since ink is transferred out of the cells of an anilox roll, if the ink does not spread after deposition, a pattern of the anilox cells will be visible in the deposited ink. This is largely due to the fact that most of the ink transfers out of the center of the cell and little ink transfers from the lands (top surface of the cell walls) of the anilox cells.
Current anilox inking systems may set up the metering blade such that ink uniformly hydroplanes underneath the blade. That is, the metering blade is spatially separated from the anilox roll to allow ink to coat the roller surface, including the lands thereof. Operating an inker in this manner results in better solid area uniformity, but is somewhat difficult to control temporally, since the amount of ink that hydroplanes underneath the blade is sensitive to many factors (e.g., ink temperature, ink viscosity, amount of ink in the inker, blade pressure, blade angle).
As such, there is a need to overcome the deficiencies of conventional printing technology for printing variable data. It would be beneficial to produce digital prints of high image quality with pattern-free inking of the print media (e.g., print substrates). Ink-based digital printing is understood to refer to ink-based printing of variable image data for producing images on media that are changeable from one image to a next image with each subsequent printing on the media in an image forming process.